Retinopathy of prematurity (ROP) is a potentially blinding disease of premature infants in which retinal blood vessels fail to develop properly. A multicentered clinical trial (CRYO-ROP Study) sponsored by the National Eye Institute demonstrated that peripheral retinal ablation at a defined stage of the disease reduced the risk of unfavorable structural outcome (i.e., retinal detachment); however, over 47.1 percent of treated eyes had vision greater than 20/200 at 5 1/2 years. The CRYO-ROP Study also defined a number of risk factors for unfavorable visual and structural outcome in ROP. Despite these advances, ROP remains a leading cause of blindness in children. More effective treatment is required in order to further reduce the rate of blindness. It is hypothesized that earlier treatment of ROP will improve the visual and structural outcome in infants with ROP. Peripheral retinal ablation will be administered to infants who develop prethreshold ROP (ROP that is severe, but not as advanced as threshold ROP as defined by the CRYO-ROP Study). To minimize the risk of treating eyes unnecessarily, since ROP may regress spontaneously in some cases, we will apply a risk management analysis program (RM-ROP2) to eyes with prethreshold disease and enroll infants with a 15 percent or greater risk of an unfavorable structural outcome for treatment. The RM-ROP2 utilizes a number of risk factors to calculate the probability of an eye having an unfavorable structural outcome. Prethreshold infants with a 15 percent or higher risk of an unfavorable outcome will be randomized. One eye will receive earlier treatment and the other will receive conventionally-timed treatment, as defined by the CRYO-ROP Study if required. Outcome will be determined at a 6 month post-term ophthalmologic examination and at a 9 month post-term visual assessment examination.